Posts tagged: Cryptography

A trio of scientists have verified that results they first presented nearly 10 years ago are in fact valid, proving that they can extract a 4096-bit RSA key from a laptop using an acoustic side-channel attack that enables them to record the noise coming from the laptop during decryption, using a smartphone placed nearby. The attack, laid out in a new paper, can be used to reveal a large RSA key in less than an hour.

Parabolic microphone extracting an RSA key from a target laptop

The attack relies on a number of factors, including proximity to the machine performing the decryption operation and being able to develop chosen ciphertexts that incite certain observable numerical cancellations in the GnuPG algorithm. Over several thousand repetitions of the algorithm’s operation, the researchers discovered that there was sound leakage they could record over the course of fractions of a second and interpret, resulting in the discovery of the RSA key in use.

Their attack works against a number of laptop models and they said that there are a number of ways that they could implement it, including through a malicious smartphone app running on a device near a target machine. They could also implement it through software on a compromised mobile device of through the kind of eavesdropping bugs used by intelligence agencies and private investigators.

The developers of GnuPG have developed a patch for the vulnerability that the Israeli researchers used, implementing a technique known as blinding. The patch is included in version 1.4.16 of GnuPG. Shamir and his co-authors, Daniel Genkin and Eran Tromer, said that they also could perform their attack from a greater distance using a parabolic microphone and may also work with a laser microphone or vibrometer.

RSA’s SecurID 800 is one of at least five commercially available security devices susceptible to a new attack that extracts cryptographic keys used to log in to sensitive corporate and government networks.

Scientists have devised an attack that takes only minutes to steal the sensitive cryptographic keys stored on a raft of hardened security devices that corporations and government organizations use to access networks, encrypt hard drives, and digitally sign e-mails.

The exploit, described in a paper to be presented at the CRYPTO 2012 conference in August, requires just 13 minutes to extract a secret key from RSA’s SecurID 800, which company marketers hold out as a secure way for employees to store credentials needed to access confidential virtual private networks, corporate domains, and other sensitive environments. The attack also works against other widely used devices, including the electronic identification cards the government of Estonia requires all citizens 15 years or older to carry, as well as tokens made by a variety of other companies.

“They’re designed specifically to deal with the case where somebody gets physical access to it or takes control of a computer that has access to it, and they’re still supposed to hang onto their secrets and be secure,” Matthew Green, a professor specializing in cryptography in the computer science department at Johns Hopkins University, told Ars. “Here, if the malware is very smart, it can actually extract the keys out of the token. That’s why it’s dangerous.” Green has blogged about the attack here.

It’s this version of the attack the scientists used to extract secret keys stored on RSA’s SecurID 800 and many other devices that use PKCS#11, a programming interface included in a wide variety of commercial cryptographic devices. Under the attack Bleichenbacher devised, it took attackers about 215,000 oracle calls on average to pierce a 1024-bit cryptographic wrapper. That required enough overhead to prevent the attack from posing a practical threat against such devices. By modifying the algorithm used in the original attack, the revised method reduced the number of calls to just 9,400, requiring only about 13 minutes of queries, Green said.

Other devices that store RSA keys that are vulnerable to the same attack include the Aladdin eTokenPro and iKey 2032 made by SafeNet, the CyberFlex manufactured by Gemalto, and Siemens’ CardOS, according to the paper.

BozoCrack is a depressingly effective MD5 password hash cracker with almost zero CPU/GPU load. Instead of rainbow tables, dictionaries, or brute force, BozoCrack simply finds the plaintext password. Specifically, it googles the MD5 hash and hopes the plaintext appears somewhere on the first page of results.

It works way better than it ever should.

How?
Basic usage:

$ ruby bozocrack.rb my_md5_hashes.txt

The input file has no specified format. BozoCrack automatically picks up strings that look like MD5 hashes. A single line shouldn’t contain more than one hash.

Researchers have decomposed a 768-bit number with 232 decimal places into its two prime factors and published a paper with their results. The number is the string released as “RSA-768″ under the now defunct RSA Challenge. As a result, RSA encryptions with 768-bit keys must, from now on, be considered cracked.

It took the team of researchers from Switzerland, Japan, Germany, France, the US and the Netherlands about two and a half years to perform the factorisation. The first step of the calculation, polynomial selection, required half a year on a cluster consisting of 80 PCs, while the second and considerably more labour-intensive sieving step took about two years on a cluster of several hundred computers. According to the researchers, a single Opteron processor with 2 Gbytes of RAM would have needed about 1,500 years to complete the sieving step.

As RSA-512 was cracked about a decade ago, the researchers assume that the computing power required to master RSA-1024 is likely to become available in about ten years. They therefore recommend that all 1024-bit RSA keys be decommissioned by 2014 at the latest.